Background: Annually, 4.6 million children die due to dehydration caused by diarrhoea. The World Health Organization (WHO) initiated the diarrheal disease control programme in 1980. In 2012, each day 1600 under five children died due to diarrhoea. It accounts for 9% of all under– five deaths. In India, acute diarrheal disease accounts for 8% death in under– five age group. Objective: To find the prevalence of diarrhoea among Rotavirus immunized and non–immunized under– five children. Materials and Methods: Hospital based cross sectional study conducted on 100 parents of children under– five years of age attending Paediatric services, in a tertiary care centre, South Kerala. Data was entered in excel and analysed using SPSS– version 16 software.  Chi Square test was used. A p–value < 0.5 was considered statistically significant. Result:  The study included 100 respondents, of which 74% children were immunized against Rotavirus and 26% were non– immunized. Out of the immunized children, 53 (71.6%) children didn’t have further episodes of diarrhoea after vaccination. The study revealed that, out of the 26 non vaccinated children, 21 children’s parents were unaware of the Rotavirus vaccine ie, 80.7% of the respondents. This indicates that the Rotavirus vaccine is not that popular among the rural population. Conclusion: Rotavirus vaccine was found to be effective in reducing the burden of diarrhoea among under– five children. Based on this study we can recommend that Rotavirus vaccination of infants be included in all National immunization programmes.